Personal mobile devices can perform communication in a manner of establishing a low-rate wireless personal area network (hereinafter abbreviated LR-WPAN).
As an example of the LR-WPAN, there exists a network following IEEE 802.15.4 standard. The IEEE 802.15.4 standard provides transmission speed of 20 Kbps and 40 Kbps in 868/915 MHz band using BPSK (binary phase-shift keying) and provides transmission speed of 250 Kbps in 2.45 GHz band using O-QPSK (offset quadrature phase-shift keying). IEEE 802.15.4b standard provides transmission speed of 250 Kbps 868/915 MHz band using O-QPSK.